One known approach for sharing data between two parties involves using a symmetric key algorithm, according to which the same cryptographic keys for both encryption and decryption of data is used. For example, if a sender wants to send a private text message to a recipient, the sender uses a shared key, known to both parties, to encrypt the message employing a symmetric encryption algorithm, such as an Advanced Encryption Standard (AES), Triple Data Encryption Standard (3DES), International Data Encryption Algorithm (IDEA), or the like. Then, the sender encrypts the shared key with the recipient's public key and sends the encrypted shared key to the recipient. The recipient decrypts the encrypted key with her private key to obtain the shared key and uses it to decrypt the private message. However, one shortcoming of this approach is that an attacker can intercept the encrypted message and use a brute force technique to guess the shared key, thereby decrypting the encrypted message without obtaining the key from the sender. An assumption of this approach is that the attacker knows which algorithm is used to encrypt the message, which can also be guessed by the attacker.
Thus, there is a need to improve the traditional symmetric key algorithm for sharing private data between parties such that an attacker cannot easily guess the shared key and/or the encryption algorithm used.